Discussions about datacentre efficiency tend to focus on the amount of power a facility consumes to run its servers and cooling apparatus, rather than how much heat these sites typically generate – and waste.

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Although there are a few notable exceptions, for many datacentre operators, the most “efficient” way of dealing with this waste heat is to release it into the atmosphere, says Roger Keenan, managing director of Shoreditch-based colocation provider City Lifeline.

“Air gets taken into the server at 25°C before getting heated up and pumped out again at 35°C and what you end up with is a very high volume of air, moving very slowly, which is slightly warm, rather than hot,” Keenan tells Computer Weekly.

Such masses of slow-moving warm air are not suited to travelling long distances, which makes it difficult for operators to redistribute it without spending huge sums of money on exchangers and recovery equipment.

“For many datacentres, the most efficient thing to do is chuck [the heat] out into the atmosphere and waste it, rather than spend a load of money on a plant that could turn it into something useful,” says Keenan.

“It’s not impossible, but it is difficult, expensive and often inefficient to pump large amounts of warm air into a block of flat or offices.”

That is, of course, unless the datacentre is next door to somewhere that can make use of the heat, as is the case for Kent-based colocation provider Custodian Datacentres.

Heat reuse in action

For the past seven years, the warm air generated by Custodian’s datacentre halls has been recycled and used to heat the offices and television studio that share the company’s site.

The air is effectively used to pre-heat these premises, raising the base-level temperature and, in turn, reducing the site’s overall central heating costs by about 30%.

“There is a cost-saving element to it, but environmentally it would be a crime not to use it, because it doesn’t make any sense for us to use tonnes of energy and just waste the end products,” says Leonard Kay, head of sales at Custodian.

Location plays a big part in Custodian’s ability to do this, along with the fact that it owns, operates and manages the site itself, while many of its competitors lease theirs, says Kay.

“We have complete control of the infrastructure, and we have our own building and maintenance teams too, which makes us far more agile and flexible than some of the other players out there to do something like this,” he adds.

A larger-scale example of a datacentre heat reuse scheme is the one operated by Russian search engine Yandex, whose facility in southern Finland provides the local community with warm water via the country’s district heating system.

Cold water is fed into the datacentre’s heat exchange system where the hot air generated by its servers is pumped in, warming the water to 30-45°C. It then passes into a heat recovery plant that further boosts the temperature to 55-60°C, before being piped to local residents.

Again, the facility’s location plays an important part in enabling Yandex to do this – the site is close to a key connection point to the district heating system, says Alexey Zhumykin, the firm’s head of datacentres maintenance.

“I wouldn’t say we had a special plan in place to do this, but in Finland there is a really big interest in green technologies, and our community is really interested in that,” he says. “Our design team is also from the Netherlands, and from the very beginning asked us to consider the possibility of making heat reuse a feature of the site.”

The setup is expected to cut heating costs by 5% for local residents over the coming year, while halving the gas consumption of nearby utility providers.

“This was a side project for us, but we’ve got a lot of benefits for operating a green datacentre, and it does work out cheaper [for residents] to buy heat from us,” says Zhumykin.

Yandex is now planning to include the technology in its next datacentre, which is under construction in Russia, he adds.

Back in 2009, a similar district heating-focused project was proposed by London-based colocation provider Telehouse, with the company announcing plans to include a heat exchanger in its soon-to-be-built Docklands facility.

It was widely reported at the time that the company was given the green light to proceed with the build on the condition that it agreed to export its waste heat to nearby homes and businesses.

The company’s marketing materials reference the fact that there is a heat exchanger on site, but it is currently unclear how many homes or businesses are benefiting from its output.

Computer Weekly repeatedly contacted Telehouse for clarification on this point, but had not received a response at the time of publication.

Barriers to adoption

Even if they are in a good location, there are other factors that make it difficult for datacentre operators to reuse their excess heat, says Professor Ian Bitterlin of the University of Leeds’s school of mechanical engineering.

“The energy density of a datacentre is 30-50 times that of an office space, so if you want to heat your offices from your datacentre waste heat, the datacentre has to be quite small or the offices need to be very large,” he says.

“A typical datacentre also operates 24/7 at a fairly constant load, and if your heat load can’t absorb the waste heat continuously, then the payback you get from a heat use scheme quickly fades away.”

Energy-effectiveness is not a key driver for datacentres. The point is that the cost of energy is not a number one agenda item for most users
Professor Ian Bitterlin, University of Leeds

In a recent interview with Computer Weekly, Ricky Cooper, vice-president for Europe, the Middle East and Africa at colocation provider Digital Realty, explained how the datacentre industry’s track record on emissions and energy consumption was attracting the attention of regulators.

“If you look at the future with driverless cars, the internet of things and the growth of connected devices in medicine, you are going to need more datacentres,” said Cooper. “The sector is exploding at the moment, but we’re only at the start.

“We’ve got higher emissions than the airline industry now, and that’s already tightly regulated. So it’s just a matter of time before the same happens to the datacentre sector – but how do you prepare for that?”

Not considered essential

Bitterlin says heat reuse is still some way off becoming common practice in the datacentre industry, simply because it is not considered an essential part of running a datacentre.

He cites figures that suggest each kWh of energy that passes through a server costs the user about 17 pence in electricity costs, but enables about £35 worth of business.

“Energy-effectiveness is not a key driver for datacentres,” he says. “The point is that the cost of energy is not a number one agenda item for most users.”

Indeed, despite the operational efficiencies brought by Custodian’s heat reuse and fresh-air cooling initiatives, Kay admits that the resilience of its datacentre is a higher priority for customers.

From our point of view, it has just always made sense to reuse our heat because it isn’t difficult to do, aside from not wanting to damage the environment our kids will inherit
Leonard Kay, Custodian Datacentres

“I don’t think our efficiency has ever won us a customer because our industry is more concerned with resilience, but as the amount of energy this industry consumes continues to grow, it will become more of a focus,” he says.

“But, from our point of view, it has just always made sense to reuse our heat because it isn’t difficult to do, aside from not wanting to damage the environment our kids will inherit.”

Opportunities in edge datacentres

One area where heat reuse schemes might be adopted more widely is edge datacentre builds that are located next to commercial or residential properties, says Bitterlin.

The edge datacentre concept – whereby a number of smaller facilities are built to accommodate data processing close to the source – is gathering pace, with web-scale internet companies favouring this approach to serve popular pieces of content to web users from nearby locations.

Digital Realty’s Cooper says that given the number of inner-city datacentres in need of refurbishment and upgrades, there is mileage in the idea of combining an edge facility with a commercial property build.

But Christopher Brown, senior vice-president for tier standards at datacentre efficiency advisory group The Uptime Institute, says it is still early days, and as long as the costs involved with rolling out an effective and efficient heat reuse scheme remain so high, mainstream adoption is still a long way off.

“I don’t think we are quite there yet, but it depends on the business goal,” he says. “At this point in time, the use of waste heat recovery in air handling systems has not proven to provide the economic benefit to justify the cost of implementation.”

Can you retrofit an existing datacentre with heat reuse technology?

What the Custodian and Yandex examples have in common is that their datacentres were built from the start with heat reuse in mind.

But trying to introduce similar technology to an existing site is unlikely to make economic sense for most operators, says Christopher Brown of The Uptime Institute.

For an effective configuration, an organisation is likely to need to plan the system from the very beginning, unless the site has a lot of spare space to work with,” he says.

Along with space requirements, the construction costs to refit a facility can far exceed the cost savings from operating the waste heat recovery technology and equipment.”

But from a corporate social responsibility or public relations point of view, there may be instances where it makes sense to deploy such technology, even if the economic benefits are negligible, adds Brown.

There are cases where a business goal might be to implement energy-efficient technology even if marginally beneficial or even slightly costly, in which case this might be an option to consider.

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